GENIUS FORUMS

I signed up for a philosophy course called: Deductive Logic.

My professor, Peter Schotch is basing the class on a book he wrote:

Intro to Logic and its Philosophy

If any of you have the time to go through the very short first chapter and maybe a bit of the second chapter, I'd be curious to here your impression of this book.

As for what my impression of it is, I'm still trying to make my way through Chapter 2. I'm having a very difficult time understanding what he is trying to say.

Schotch, Chapter 2, Pg. 8 wrote: "Sometimes, for some pieces of reasoning, human beings find the move from premises to conclusion compelling. Why is that? What explains this compulsion? We earlier made an attempt to answer this question in terms of an account of rationality"

^ The part at the end that I bolded is what I'm confused about.

Where this "earlier attempt to answer the question via an account of rationality" is, is not something I can clearly identify.

My best guess is that it is back a few sentences, near the top of page 8, where Schotch writes:

"Nobody who understands the sentences can sincerely tell us that C, the conclusion, doesn’t follow from P1 and P2, the premises.(paraphrased)"

^ That must be what Schotch regards as both an account of rationality as well as the 'earlier' attempt to answer the question: "why are we compelled to move from the premises to the conclusion in the typical way that we do?"

But in my view, he isn't accounting for rationality, nor does he answer the question as to why people are compelled to regard the inference as correct. All he is doing is saying that people are simply compelled to do so. He is simply stating an observation that most people react in a similar way when faced with such an inference, as opposed to a true account, which would explain 'why' they do it.

On pg. 9 he says:

"We earlier made an attempt (on pg. 8) to answer this question in terms of an account of rationality. On that view, It would be irrational to accept the John and Mary premises, and not accept the conclusion."

On that view? What view is he refering to?

Perhaps it is this one:

"Nobody who understands the sentences can sincerely tell us that C, the conclusion, doesn’t follow from P1 and P2, the premises."

^ But is that really an account of rationality?

To make matters more confusing, Schotch goes on to say:

"it would be as irrational [to deny the final conclusion of the John/mary inference] as it would be to accept that John is happy and also not to accept it (at the same time)."

Why?

One problem I see is that Schotch accounts for rationality based on how people generally react to a proposed deductive inference, yet when he tries accounting for irrationality, he bases such an account on how no one reacts to a proposed inference. Surely we can come up with a better account for irrationality than the non-manifesting phenomena of people accepting and denying a premise simultaneously! Since we are basing our definition of rationality on observed phenomena, shouldn't we do the same for our definition of irrationality?

Schotch goes on to say:

We should notice however, that we do not yet have an account of the ‘as irrational as’ relation.

An account of the 'as irrational as' relation? What??

Did Schotch actually establish a clear account of rationality or irrationality?

Schotch goes on to say:

Contemporary logic actually has two of such accounts [of the 'as irrational as']. These two correspond to the two theories of logical consequence or, more informally, of the 'follows from' relation.

The second kind of explanation which might be offered here — is one that has little or nothing to do with reasoning, at least directly: We are thinking here of a biological, or evolutionary explanation. It could have been the case, hundreds or thousands of generations ago, that there existed a tribe of proto-humans who did not in fact feel compelled (due to irrationality?) to accept the conclusion of the John and Mary type of inference even after they had accepted the premises. But these hapless folk were all eaten by cave bears or other predators before their civilization could develop.

Ok, so these proto-humans are supposed to be an example of irrationality? I don't see how it relates to the 'as irrational as' relation.

Actually I'm not even sure what the 'as irrational as' relation, as a concept, even means.

Some help with this would be much appreciated.

probably be best to go up to him and ask questions regarding his book

average wrote:probably be best to go up to him and ask questions regarding his book

Yes, I was planning to do that, but since I can't see him 'till Monday, I figured I'd try to see if I'm not the only one who finds his writing extremely opaque.

I think that is the general idea. He makes it plain in his writing that he has no real desire to get the heart of matters.

-

I also want to add that the intro to his book hinges largely on the following inference:

(P1) John is happy.
(P2) If John is happy, then Mary is sad.
(C) Therefore, Mary is sad.

With the above inference stated, the most basic point Schotch seemed to emphasize earliest on, was that it would be irrational to accept the John and Mary premises, and not accept the conclusion.

But my problem was with the logic of accepting premises. If a conclusion logically follows from illogical premises, then is the conclusion logical? For instance: Who is John? How do we know he is happy? And most importantly, what reasons do we have to believe that whenever he is happy, Mary must be sad? It doesn't seem logical to just blindly accept these premises.

Schotch in his book says:

Sometimes, for some pieces of reasoning, human beings find the move from premises to conclusion compelling.

That being said, I guess there are humans like me who find the move from non-premise to premise compelling. I just don't see why it's logical to value conclusions which are based on premises that don't make sense (e.g., If John is happy, then Mary is sad)

If you want to introduce logic, you should begin with the very essence of logic: establishing premises.

Schotch immediately sidesteps this issue, proceeding to write his way into what I can only regard as impenetrable fog. Chapter 2 makes no sense to me.

Cory Duchesne wrote:It doesn't seem logical to just blindly accept these premises.

Then don't blindly accept them. Accept them because your professor told you to accept them. I think you're forgetting that he created the premises for the purpose of making a point and consequently are taking them out of context.

From the book:

Logic is the science of reasoning, pure and simple.

I think logic is the practice of thinking with consistent ideas. I think that about covers it.

Cory Duchesne wrote:Some help with this would be much appreciated.

The guy is lost and he's not really saying anything. He clearly has no idea what logic or rationality is. If you want to pass this class you'll probably have to just memorize the categories that he likes and reiterate them when he indicates that you're supposed to do that.

preservationist picture = Going from premises to conclusion in those inferences preserves truth.

syntactic perspective (also called the proof theoretic perspective) = the follows-from relation is reconstructed as the relation of provability

semantic perspective (also called the model theoretic perspective) = the follows-from relation as the relation of semantic entailment

provability = . . .

semantic entailment = . . .

Etc., etc. That chapter might not even matter since the book is about symbolic logic and it might have been written only because he thought the book should open up with some prose.

Have fun! :-)

A real logic book would open up with:

The Cow that can be told is not the eternal Cow.

Matt Gregory wrote:

Cory Duchesne wrote:It doesn't seem logical to just blindly accept these premises.

Then don't blindly accept them. Accept them because your professor told you to accept them.

You're basically saying: don't blindly walk into a wall. Walk into a wall because someone told you to walk into a wall. Gee, thanks a lot!

I think you're forgetting that he created the premises for the purpose of making a point and consequently are taking them out of context.

He created the premises for the purpose of introducing what he believes is logic. However, I am not yet convinced that it is really logic that he's introducing.

You're basically like saying: don't blindly walk into a wall. Walk into a wall because someone told you to walk into a wall. Gee, thanks a lot!

No, I'm saying that trying to place the premises in a "real world" context is deluded, because the real world is actually the lesson that he's trying to teach.

Ironically, logic professors are always incorrigibly illogical, and an honest man’s marks will always suffer for it… btw Cory, good luck with that course old boy… : )

Matt Gregory wrote:

You're basically saying: don't blindly walk into a wall. Walk into a wall because someone told you to walk into a wall. Gee, thanks a lot!

No, I'm saying that trying to place the premises in a "real world" context is deluded

I'm not insisting that he do that. I'm saying that the act of generating a premise is the most fundamental of logical operations, and thus, if he wants to introduce logic, then he should first spend time on what it means to generate a premise. He is actually avoiding this issue, and proceeding to write a very long book in a very opaque manner.

the real world is actually the lesson that he's trying to teach.

I'd like to hear how you came to this conclusion. To me, it seems like he's trying to teach the opposite of the real world.

I don't know if he's teaching about the real world or not, since I haven't taken his class. I'm saying you are trying to depart from the real world. The lesson is what you are experiencing, not Mary or John or whatever, therefore the lesson is as real as it gets.

But the way I look at it, you paid money to take his class and in my experience of university you get what you pay for. If you want to get a good grade you need to take what he's offering. If you go in there trying to change the lessons then you're probably going to be miserable and not do as well. If you don't like it, you should drop the class.

Now I'm not saying that you should suppress your own thoughts about it, but maybe you should keep your thoughts separate from school by writing them in a journal or something and save them for later. Maybe you could write up a good article about the guys flaws or something when the class is over. I used to question my professors all the time and I didn't do very well in school. If I were to go again, I would just conform to the professors and try to do what they wanted me to do. School isn't about thinking. Nobody wants you to think freely at school, they want you above all to conform. But I think there's value in having the ability to conform to circumstances when the need arises. It's not good to be totally undisciplined.

Cory Duchesne wrote: I'm saying that the act of generating a premise is the most fundamental of logical operations, and thus, if he wants to introduce logic, then he should first spend time on what it means to generate a premise.

Possibly, but that is not what symbolic logic is about. "Forming premises" is outside the scope of symbolic logic.

Symbolic logic should be thought of as a "content free grammar" - that is, given certain premises (whatever they are) what statements that can be deduced from them? What are the rules of logic? This is easier to examine without the distraction of the meaning of various propositions, by looking at just the structure of the argument. By extracting what kind of conclusions are valid, we can later apply these in specific cases to avoid various classes of errors in thinking.

Symbolic logic is very artificial - for instance, every statement is usually taken to be either completely true or completely false, with no other possibility. But this is the simplest case, so it is the easiest to study. I personally think it is a very worthwhile study. It is a very strong starting point.

You seem to be faulting your teacher for teaching the subject, rather than something else. That "something else" may well be more fundamental, more important, or something you are more interested in - but it is not the class you have signed up for. Your teacher (or other advisor) may be able to steer you to other classes that are more geared to your interests.

Matt Gregory wrote:I don't know if he's teaching about the real world or not, since I haven't taken his class. I'm saying you are trying to depart from the real world. The lesson is what you are experiencing, not Mary or John or whatever, therefore the lesson is as real as it gets.

But the way I look at it, you paid money to take his class

Well, I haven't yet actually. I can drop his class within the next two weeks. I probably will.

and in my experience of university you get what you pay for.

I have no regrets about the courses I took last year, they served as a good introduction to somethings I might not have considered.

I'm frustrated about this deduction course because I can't understand his opening prose. It's just incredibly dense writing. I am open minded that maybe I'm just missing something. We'll see.

If you want to get a good grade you need to take what he's offering.

Or I can turn it down and focus on my other five classes.

If you go in there trying to change the lessons then you're probably going to be miserable
and not do as well.

You're right about that. I've gotten into some trouble last year, being too outspoken really makes for a rough year.

If you don't like it, you should drop the class.

I probably will.

Now I'm not saying that you should suppress your own thoughts about it, but maybe you should keep your thoughts separate from school by writing them in a journal or something and save them for later. Maybe you could write up a good article about the guys flaws or something when the class is over. I used to question my professors all the time and I didn't do very well in school. If I were to go again, I would just conform to the professors and try to do what they wanted me to do.

I can understand where you're coming from and already I'm experiencing a bit of stress from the degree to which I've question him so far.

School isn't about thinking. Nobody wants you to think freely at school, they want you above all to conform. But I think there's value in having the ability to conform to circumstances when the need arises.

This I'm not so sure about. I'll think about it.

DHodges wrote:

Cory Duchesne wrote: I'm saying that the act of generating a premise is the most fundamental of logical operations, and thus, if he wants to introduce logic, then he should first spend time on what it means to generate a premise.

Possibly, but that is not what symbolic logic is about. "Forming premises" is outside the scope of symbolic logic.

Symbolic logic should be thought of as a "content free grammar" - that is, given certain premises (whatever they are) what statements can be deduced from them? What are the rules of logic?

What is the use in doing this?

[logic] is easier to examine without the distraction of the meaning of various propositions, by looking at just the structure of the argument. By extracting what kind of conclusions are valid, we can later apply these in specific cases to avoid various classes of errors in thinking.

Hmmm. This is the hump I need to get over. I don't understand what you're saying there.

Symbolic logic is very artificial - for instance, every statement is usually taken to be either completely true or completely false, with no other possibility. But this is the simplest case, so it is the easiest to study. I personally think it is a very worthwhile study. It is a very strong starting point.

I don't really see why it's a strong starting point, because it's not the foundation of logic. A strong starting point is starting with the foundation.

You seem to be faulting your teacher for teaching the subject, rather than something else.
That "something else" may well be more fundamental, more important, or something you are more interested in - but it is not the class you have signed up for. Your teacher (or other advisor) may be able to steer you to other classes that are more geared to your interests.

Ok, fair enough Dave.

I actually addressed some of my qualms on a class discussion board.

Schotch swooped in and responded:

As for premises which don't make sense, whatever exactly that means (and it can mean lots of different things), it is part of the viewpoint of classical logic that any (grammatical) sentence whatever can serve as a premise. That may seem stupid to you, since you won't have any occasion to reason from some premise that doesn't make sense. On the other hand, "makes sense" is hardly universal. What makes sense to me, will in many cases not make sense to you. So logic has no choice but to allow the widest possible interpretation.

In my experience, when accounting for my own illogical behavior, as well as for the illogical behavior of others, I find that illogic stems from believing in things that feel good and denying things that feel bad. It really isn't about 'making sense', it's about feeling good.

Cory Duchesne wrote:

DHodges wrote:[logic] is easier to examine without the distraction of the meaning of various propositions, by looking at just the structure of the argument. By extracting what kind of conclusions are valid, we can later apply these in specific cases to avoid various classes of errors in thinking.

Hmmm. This is the hump I need to get over. I don't understand what you're saying there.

Symbolic logic is the study of how arguments work - what is valid reasoning.

If I say: "A is true because I really want A to be true," it's easier to discuss objectively why this is not a good argument. If you started with "God exists because I really want there to be a God," then you will likely get distracted by theological or emotional issues which are actually irrelevant - it's structurally not a good argument, and that has nothing to do with the nature of God, or if you really really want it.

On the other hand, we can see that an argument like "All apples are red, John has an apple, therefore John's apple is red" is a valid argument. As you pointed out, this does not address the issue as to whether the premises are true - there might be green apples, John might actually have a pear. Those are empirical questions that must be investigated, not questions about what is valid reasoning.

In science, you might have reasoning like: "If theory A is true, then at an energy of 10 MeV I should see a particle with these properties." If you then go to that energy and find the predicted particle, that is strong evidence in favor of theory A, while finding a particle with different properties would be strong evidence that theory A is flawed.

I don't really see why it's a strong starting point, because it's not the foundation of logic. A strong starting point is starting with the foundation.

Well, consider an analogy with learning something else. When you start learning mathematics, you start with the integers, addition, subtraction, multiplication - not because these are fundamental, but because they are easy to grasp. You could start with abstract algebra, defining what elements of a set are and what it means for a set to be closed under an operation before considering the specifics of addition - but for most people, that would not be an appropriate way to learn math.

Same with physics - you actually can't start with the fundamentals, because there is no known complete Theory of Everything. You start with things that are easy to grasp and easy to demonstrate. You work out from there.

Sometimes, the foundations are not where you need to start - because you will have no idea of what you are learning the foundations of. It makes more sense later on. You start with things that are easier to grasp and are more immediately useful.

I totally know what you're going through, Cory. I was the exact same way, except for me the breaking point was in linear algebra and I was just like "WTF! Why would I want to know this!? Eigenvalues? Dot products? WTF?" I had this conversation with the professor that went something like:

Me: What is the purpose of a vector? Isn't it just a list of numbers?

Him: Say you wanted to describe the location of an item in a store. You could take the aisle number and call it 'x', then take the position down the aisle and call it 'y', then take the shelf number and call it 'z', then you would have a vector of 'x, y, z'.

Me: In other words, a list of numbers.

Him: Well, that definition would be very narrow!

Me: Erm...

Matt Gregory wrote:In other words, a list of numbers.

A vector is not just a list of numbers. It's a list of numbers in a particular order.
You don't think that's the most bitchenest thing in the history of the universe?!

Him: Well, that definition would be very narrow!

Duh, a vector is one-dimensional.



[/ extreme math nerdism]

LOL

DHodges wrote:[/ extreme math nerdism]

That's okay, seeing as this is "Genius Forum". You might as well call it "Big Nerd Forum".

Matt Gregory wrote:But I think there's value in having the ability to conform to circmstances when the need arises. It's not good to be totally undisciplined.

Yeah, yeah, I agree, I agree, I agree. Totally agree (that is very important on the net: always agree, agree, agree). Better go to school before ending up a total failure like Naturyl; I feel for him, I really do, but in the end, he pissed his life away (thinking about it, he could still change, but I don't think it is going to happen).

So yeah, go to school. More schooling is important, it makes you immortal. Most people will be forgotten when they die -- as if they were never born, never lived. They just go *poof* and that was it. No one to chronicle their life, they just disappear and no one is there to remember them. I don't mean *every* waking hour, of course not. I mean leaving behind *something* of value for which they will be remembered. Not some forum posts or something -- they will disappear anyway, relying on the net is a bad idea. For example, the people on here called QRS, too, will be forgotten: they did not further their careers, totally depending on the net. Without the net, they would be totally unknown and forgotten -- in vain, oh, in vain it has all been!
In this regard, the Mr. Phil O. Sopher will not be forgotten -- great minds like Quine, who really worked hard: not lazy ones like Naturyl, who don't do a damn thing but surf the internet (he rationalizes it quite a bit: poor soul) -- so in this regard, go to school, take classes, learn all they require from you and try to make this life your parents forced upon you (worse enough!) a life worth to be remembered.